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.TH "MPI_WIN_LOCK" "3" "Jul 22, 2024" "" "Open MPI"
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.sp
\fI\%MPI_Win_lock\fP — Starts an RMA access epoch locking access to a
particular rank.
.SH SYNTAX
.SS C Syntax
.INDENT 0.0
.INDENT 3.5
.sp
.nf
.ft C
#include <mpi.h>

int MPI_Win_lock(int lock_type, int rank, int assert, MPI_Win win)
.ft P
.fi
.UNINDENT
.UNINDENT
.SS Fortran Syntax
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.INDENT 3.5
.sp
.nf
.ft C
USE MPI
! or the older form: INCLUDE \(aqmpif.h\(aq
MPI_WIN_LOCK(LOCK_TYPE, RANK, ASSERT, WIN, IERROR)
     INTEGER LOCK_TYPE, RANK, ASSERT, WIN, IERROR
.ft P
.fi
.UNINDENT
.UNINDENT
.SS Fortran 2008 Syntax
.INDENT 0.0
.INDENT 3.5
.sp
.nf
.ft C
USE mpi_f08
MPI_Win_lock(lock_type, rank, assert, win, ierror)
     INTEGER, INTENT(IN) :: lock_type, rank, assert
     TYPE(MPI_Win), INTENT(IN) :: win
     INTEGER, OPTIONAL, INTENT(OUT) :: ierror
.ft P
.fi
.UNINDENT
.UNINDENT
.SH INPUT PARAMETERS
.INDENT 0.0
.IP \(bu 2
\fBlock_type\fP: Either MPI_LOCK_EXCLUSIVE or MPI_LOCK_SHARED (state).
.IP \(bu 2
\fBrank\fP: Rank of locked window (nonnegative integer).
.IP \(bu 2
\fBassert\fP: Program assertion (integer).
.IP \(bu 2
\fBwin\fP: Window object (handle).
.UNINDENT
.SH OUTPUT PARAMETER
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.IP \(bu 2
\fBierror\fP: Fortran only: Error status (integer).
.UNINDENT
.SH DESCRIPTION
.sp
Starts an RMA access epoch. Locks ensure that only the windows created
by specific processes can be accessed by those processes (and by no
other processes) during that epoch.
.sp
Locks are used to protect accesses to the locked target window effected
by RMA calls issued between the lock and unlock call, and to protect
local load/store accesses to a locked local window executed between the
lock and unlock call. Accesses that are protected by an exclusive lock
will not be concurrent at the window site with other accesses to the
same window that are lock protected. Accesses that are protected by a
shared lock will not be concurrent at the window site with accesses
protected by an exclusive lock to the same window.
.sp
The \fIassert\fP argument is used to provide assertions on the context of
the call that may be used for various optimizations. (See Section 6.4.4
of the MPI\-2 Standard.) A value of \fIassert\fP = 0 is always valid. The
following assertion value is supported:
.INDENT 0.0
.TP
.B MPI_MODE_NOCHECK
No other processes will hold or attempt to acquire a conflicting lock
while the caller holds the window lock.
.UNINDENT
.SH NOTES
.sp
In a client/server environment in which clients connect to a server and
create windows that span both the client and the server, if a client or
server that has obtained a lock on such a window and then terminates
abnormally, the server or other clients may hang in a \fI\%MPI_Win_lock\fP call,
failing to notice that the peer MPI job has terminated.
.SH ERRORS
.sp
Almost all MPI routines return an error value; C routines as the return result
of the function and Fortran routines in the last argument.
.sp
Before the error value is returned, the current MPI error handler associated
with the communication object (e.g., communicator, window, file) is called.
If no communication object is associated with the MPI call, then the call is
considered attached to MPI_COMM_SELF and will call the associated MPI error
handler. When MPI_COMM_SELF is not initialized (i.e., before
\fI\%MPI_Init\fP/\fI\%MPI_Init_thread\fP, after \fI\%MPI_Finalize\fP, or when using the Sessions
Model exclusively) the error raises the initial error handler. The initial
error handler can be changed by calling \fI\%MPI_Comm_set_errhandler\fP on
MPI_COMM_SELF when using the World model, or the mpi_initial_errhandler CLI
argument to mpiexec or info key to \fI\%MPI_Comm_spawn\fP/\fI\%MPI_Comm_spawn_multiple\fP\&.
If no other appropriate error handler has been set, then the MPI_ERRORS_RETURN
error handler is called for MPI I/O functions and the MPI_ERRORS_ABORT error
handler is called for all other MPI functions.
.sp
Open MPI includes three predefined error handlers that can be used:
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.IP \(bu 2
\fBMPI_ERRORS_ARE_FATAL\fP
Causes the program to abort all connected MPI processes.
.IP \(bu 2
\fBMPI_ERRORS_ABORT\fP
An error handler that can be invoked on a communicator,
window, file, or session. When called on a communicator, it
acts as if \fI\%MPI_Abort\fP was called on that communicator. If
called on a window or file, acts as if \fI\%MPI_Abort\fP was called
on a communicator containing the group of processes in the
corresponding window or file. If called on a session,
aborts only the local process.
.IP \(bu 2
\fBMPI_ERRORS_RETURN\fP
Returns an error code to the application.
.UNINDENT
.sp
MPI applications can also implement their own error handlers by calling:
.INDENT 0.0
.IP \(bu 2
\fI\%MPI_Comm_create_errhandler\fP then \fI\%MPI_Comm_set_errhandler\fP
.IP \(bu 2
\fI\%MPI_File_create_errhandler\fP then \fI\%MPI_File_set_errhandler\fP
.IP \(bu 2
\fI\%MPI_Session_create_errhandler\fP then \fI\%MPI_Session_set_errhandler\fP or at \fI\%MPI_Session_init\fP
.IP \(bu 2
\fI\%MPI_Win_create_errhandler\fP then \fI\%MPI_Win_set_errhandler\fP
.UNINDENT
.sp
Note that MPI does not guarantee that an MPI program can continue past
an error.
.sp
See the \fI\%MPI man page\fP for a full list of \fI\%MPI error codes\fP\&.
.sp
See the Error Handling section of the MPI\-3.1 standard for
more information.
.sp
\fBSEE ALSO:\fP
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.INDENT 3.5
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.IP \(bu 2
\fI\%MPI_Win_unlock\fP
.IP \(bu 2
\fI\%MPI_Win_lock_all\fP
.UNINDENT
.UNINDENT
.UNINDENT
.SH COPYRIGHT
2003-2024, The Open MPI Community
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